This protest is young people discovering their voice. It's a wonderful thing.
As far as the violence goes:
I've heard a number of reasonable people questioning whether violent protesting is a good thing or a bad thing. They frequently point to the Stonewall Riots as evidence for the long-term morality of violent protesting.
http://en.wikipedia.org/wiki/Stonewall_riots
Sadly, creating violence can make decisions easier for authorities, because based on simply "minimizing harm" considerations, they can make decisions in the interests of violent protestors.
Nowadays, I tell them its a bad thing, because it's very unfair to the innocents that get damaged. "Do no harm" is a more moral philosophy than the "Ends justify the means" because you never actually have all the knowledge, and you can't know if an apparently morally wrong action is going to lead to good consequences or not. Thus, we shouldn't take unnecessary risks.
However, if government persistently refuses to acknowledge what people want, and conditions are unacceptable, then their hand is forced and violence is justified. But it's not at that point, and I don't think Obama's administration is headed in that direction, considering his public statements on the perceived racism problem.